Band-gap tunability of a (6,0) BN nanotube bundle under pressure: Ab initio calculations

Ab initio calculations were performed to study the structural transformation on a boron nitride nanotubes bundle under pressure. Several bundles of boron nitride nanotubes, disposed into a hexagonal arrangement, were studied between which the (6,0) zigzag configuration was chosen to be detailed here. Upon compression the hexagonal arrangement as well as the circular cross section of the tubes were preserved up to a critical pressure value. At this pressure value the tubes deform to an oval cross section and the bundle shape diverge from the original hexagonal symmetry. The percent difference volume suffers a discontinuity with pressure demonstrating the discontinuous nature of the structural transition. The energy gap undergoes a continuous decrease up to the pressure of collapse of the tubes. The tunability of the gap is a fundamental requirement for engineering electronic nanodevices widening the perspectives for boron nitride nanotube applications.